Re: Sessions, it feels like ages since Trump started criticizing him on Twitter, and it's been on a semi-regular basis; it wouldn't surprise me to see the Sessions mention count hovering in the top 5 to top 10 (after Obama, Hillary, and Mueller of course).
So why is Sessions still in office?!
We saw Trump really dawdle with having Pruitt removed (sorry, "resigned"), but he had mostly good things to say about him in the run up to that (and there were whispers that Pruitt was being held on to specifically to replace Sessions; now I'm hearing Senator Graham is being whispered as the next AG). Outside of the Mueller investigation, Sessions has been a pretty consistent champion of Trump's and the GOP's policies on immigration, rolling back the movement to investigate and contain police violence, reverse course on many pending lawsuits in a number of other social and regulatory areas. Trump really seems petty enough to me, though, that despite all that Sessions has done for him and the GOP, Trump wouldn't care if there was just one area (Russia) where Sessions failed to display total loyalty.
I know that there was an assumption that Sessions had some degree of protection due to his Senate past, and with Trump basically needing no Senate defections to carry out legislative victories, so maybe that explains it and now that Senators are turning against Sessions, we'll see him gone soon.
I kind of like the narrative that says "keep your friends close and your enemies closer" though; maybe Sessions has some sort of leverage over Trump, maybe over Russia or other crimes during the campaign, transition, and/or early presidency, that compels Trump to keep him on, even when he wants to fire Sessions.
Still begs that question of why continually call out Sessions on Twitter; maybe it's as simple as Trump really wants to keep Sessions around, but also really wants him to stop doing this one small "simple" thing (recusal), and he thinks he's going to get what he wants if he keeps badgering Sessions publicly.